59 - Prospective Evaluation of Procedural Factors Related to False Negative Fluorescence In-Situ Hybridization (FISH) in Patients with Extrahepatic Cholangiocarcinoma

Award: Outstanding Research Award in the Biliary/Pancreas Category (Trainee)

Manik Aggarwal, MBBS, Eric J. Vargas, MD, MS, John Martin, MD, Bret Petersen, MD, Aliana Bofill-Garcia, MD, Ryan J. Law, DO, Andrew Storm, MD, Barham Abu Dayyeh, MD, MPH, Vinay Chandrasekhara, MD
Mayo Clinic, Rochester, MN

Introduction: Fluorescence in-situ hybridization (FISH) is recommended as part of multi-modality sampling in evaluation of biliary strictures but is limited by sensitivity. This study aimed if sampling techniques affected the sensitivity of FISH in patients with extrahepatic cholangiocarcinoma (eCCA).

Methods: Patients undergoing tissue sampling for suspected malignant biliary strictures from Oct 20-Feb 22 were prospectively enrolled (NCT04572711). Procedural factors such as sampling techniques, order, and utilization of combination sampling was recorded. Results of an optimized pancreatobiliary FISH panel with locus specific probes for 1q21, 7p12, 8q24 and 9p21 were reported per guidelines. Negative or equivocal FISH results were considered negative in this study. FISH polysomy was considered positive for malignancy. Final diagnosis was confirmed either by histopathology, or multidisciplinary hepatobiliary tumor board using pre-determined institutional criteria, or by suggestive clinical course with minimum 12-month follow-up. Statistical analyses were performed using BlueSky Statistics v.10.3.1, R package v8.81.

Results: Of 351 patients, 74 (21.1%) were diagnosed with eCCA, of whom 31 (41.9%) had primary sclerosing cholangitis (PSC). FISH had an overall sensitivity and specificity of 63.1% and 95.2% for diagnosis of eCCA. A false negative FISH was reported in 24 (37.8%) patients with eCCA. Characteristics of patients with eCCA stratified by FISH results are depicted in Table 1. Patients that underwent stricture dilation were more likely to have a false negative FISH result (92.9% vs 73.9%, p=0.06). False negative FISH rates were similar regardless of order of sampling (whether brushing, biopsy or dilation were performed first, p=0.39) or whether brushing was performed with or without biopsy (p=0.44). On multivariable analysis, stricture dilation was associated with a significantly higher odds of false negative FISH test (OR=5.2, 95% confidence interval 1.2-35.9) (Figure 1).

Discussion: In this prospective study, dilation of strictures was associated with a higher rate of false negative FISH results in patients with eCCA. Disruption of normal biliary epithelium due to dilation may affect performance of FISH. Randomized controlled studies to define optimal sampling strategies are needed to confirm these findings.




Disclosures:


Manik Aggarwal, MBBS, Eric J. Vargas, MD, MS, John Martin, MD, Bret Petersen, MD, Aliana Bofill-Garcia, MD, Ryan J. Law, DO, Andrew Storm, MD, Barham Abu Dayyeh, MD, MPH, Vinay Chandrasekhara, MD, 59, Prospective Evaluation of Procedural Factors Related to False Negative Fluorescence In-Situ Hybridization (FISH) in Patients with Extrahepatic Cholangiocarcinoma, ACG 2023 Annual Scientific Meeting Abstracts. Vancouver, BC, Canada: American College of Gastroenterology.